With mass data storage currently falling into the terabyte range, mass data storage devices have become increasingly employed in computers and large data storage systems. Also due to the increasing amount of data to be stored, data read and write speeds have necessarily had to be improved. Such mass data storage devices include tape drives, as well as hard disk drives that have one or more spinning magnetic disks onto which data is recorded for storage and subsequent retrieval. Hard disk drives may be used in many applications, including personal computers, servers, databases, television set-top boxes, and other audio, video, or television applications.
Looking more particularly at hard disk drive systems, the disk drives included therein typically include rotating magnetic disks on which information is magnetically recorded. A head having transducers therein is movably supported adjacent the magnetic disk for reading and writing the information to and from the disks. The head typically flies above the surface of the disk so that it does not touch the surface of the disk during normal operation. Recently, magneto-resistive (MR) transducers have gained wide popularity for use on such read/write heads. The term “magneto-resistance” refers to the change in resistivity of the materials of the transducer in the presence of a magnetic field induced in the transducer by the magnetic domains recorded on the disk. The introduction of MR heads (or other appropriate materials) into disk drives has significantly increased the overall density of hard disk drive systems.
During both the read and write processes, the temperature of the read/write heads typically changes. As their temperature increases, the materials comprising the read/write transducers tend to expand, causing the head to extend towards the disk media, so-called pole-tip-protrusion (PTP). As the distance between the head and the disk media (i.e., the fly height) changes, so too does the bite-error rate (BER) of the data writing or reading operation. Typically, as the heads are positioned closer to the disk media, the BER improves. However, since PTP occurs during operation, the heads cannot be placed at the least distance from the disk media, lest they collide with the disk media as they heat-up during use. As a result, fly height control (FHC) has been developed to dynamically alter the fly height of the heads during operation, in response to detected changes in temperature, by altering the power supplied to various temperature-sensitive components in the head. Unfortunately, conventional techniques employed to detect the temperature on which the FHC is based do not typically give an actual and accurate reading at the most important point in the FHC process, the head-disk interface (HDI).